部分水解聚丙烯酰胺柠檬酸铝体系临界交联浓度的研究

采用落球粘度计、核孔膜过滤、动态光散射 (DLS)和2 7Al NMR法 ,研究了高分子量、低浓度的部分水解聚丙烯酰胺 (HPAM)与柠檬酸铝 (AlCit)体系形成交联聚合物溶液 (LPS)的临界交联浓度 .研究结果表明 ,HPAM AlCit体系在聚合物浓度较低时 ,溶液中主要发生形成交联聚合物线团 (LPC)的交联反应 ,此时形成的是LPS ,聚合物浓度增加到某一临界值后 ,体系中形成线团后 ,存在线团间的交联 ,此时形成的是弱凝胶 .不同方法所测得的HPAM AlCit体系的临界交联浓度基本相同 ,对于粘均相对分子质量为 1 4× 10 7的HPAM ,在NaCl浓度为 2 0 0 0mg L ,交联比 2 0∶1时形成的交联体系 ,其临界交联浓度在 2 0 0～ 30 0mg L间 .

THE STUDY OF THE CRITICAL CROSSLINKING CONCENTRATION FOR HPAM/AlCit SYSTEM

The critical crosslinking concentration of linked polymer solutions(LPS) formed by low concentration and high molecular weight partially hydrolyzed polyacrylamide (HPAM) and aluminum citrate (AlCit) was investigated by using dynamic viscosimetry,nuclear pore membrane,dynamic light scattering and 27Al-NMR measurements.The experimental results show that the viscosity and spin-lattice relaxation time (T 13) of HPAM/AlCit crosslinking systems decrease with reaction time in low concentrations(the concentration of HPAM is between 100 mg/L and 200 mg/L) and increase with reaction time in a high concentration (300 mg/L).The results measured by dynamic light scattering show that the mean hydrodynamic radius of linked polymer coils(LPC) is about 238 nm and 246 nm with HPAM concentrations of 100 mg/L and 200 mg/L in the solution,respectively.The filtration velocity of the LPS with HPAM concentrations of 100 mg/L and 200 mg/L in the solution is almost the same.The mean hydrodynamic radius of LPC is about 379 nm in the LPS with HPAM concentrations of 300 mg/L,and the filtration velocity of the LPS is lowered obviously.These results indicate that the linked polymer solution is formed by intra-molecular crosslinking of HPAM and AlCit forming linked polymer coils in the system of lower concentration.When the polymer concentration of HPAM/AlCit system is increased to a critical concentration,the weak gel is formed by crosslinking of LPC.The critical crosslinking concentration of LPS is between 200 mg/L and 300 mg/L for the system made up of HPAM molecular weight 1 4×107 and NaCl concentration 2000 mg/L.The critical crosslinking concentrations of the linked polymer solution measured by different methods are consistent with each other.